The present invention relates to an optical system especially adapted for use in binoculars. More particularly, the invention relates to an automatic focussing system for use with binoculars.
In the conventional set of binoculars, the focus is adjusted by separate adjustment rings provided for the ocular lenses for both of the two halves of the binoculars. These include generally a screw-threaded portion which upon manual rotation permits the ocular lenses to be moved in and out thereby changing the focal position with respect to a corresponding pair of objective lenses. Such binoculars are, for example, described in the booklet "Encyclopedia of Binoculars" published by the Japan Light Machinery Information Center, New York, N.Y., and the booklet "Binoculars and All-Purpose Telescopes", Henry E. Paul, published by AMPHOTO, New York, N.Y.
Although the well-known focussing system of the prior art was capable of adequately functioning, it was nonetheless desired to provide a binocular optical system in which the focussing position could be changed much more readily than was possible with the prior art system. It is also desirable to provide an optical system for binoculars in which it is not necessary for the ocular lenses and their supporting structure to be rotated which was frequently a source of annoyance to the user of the binoculars.
Although unknown in the binocular art, automatic focussing systems have been in the camera art, particularly in the single lens reflex camera art. For example, an automatic focussing system has been in use with cameras produced by Honeywell Co. In that system, an automatic focussing module is provided in which two unfocussed incoming light beams are reflected from opposite side of a prism with the resulting two parallel beams separately focussed and shone upon an image viewing screen. The camera lens is adjusted until the two images coincide upon the viewing screen. If desired, an automatic electronic device can be added to this system for automatically detecting when the two images coincide. Although admittedly such modules have been in use for some time in the camera art, their use has hitherto been unknown in the binocular art where, as opposed to the single lens reflex camera art utilizing a single in-line lens system, two entirely separate light paths and lens systems must necessarily be employed and these two focussed separately but in cooperation with one another.
Besides the desire for providing an automatic focussing system, it was desirable to provided binoculars in which the magnification power could quickly be adjusted without having to separately readjust the focal distance of both lens systems.
Accordingly, it is an object of the present invention to provide a binocular system in which the focal length can be changed quickly without rotation of the lens eye pieces.
Moreover, it is an object of the invention to provide such a binocular system in which the focus can be automatically adjusted as the field of view of the binoculars is changed or as the object being viewed moves.